The hydroboration reaction, discovered and explored by Professor H.C. Brown and his students, has made organoboranes readily available for the first time. The reaction exhibits a remarkable stereospecificity. Consequently, the hydroboration of dienes and trienes produces cyclic, bicyclic, and polycyclic organoboranes with defined stereochemistry. Moreover, the hydroboration reaction tolerates the great majority of functional groups. Consequently, it is now possible for the first time to synthesize functional organoboranes containing such reactive groups. These new products are of interest in themselves as materials which should be explored for their possibilities for biochemical and pharamaceutical application. In addition, methods have been developed for replacing boron by carbon. Consequently, the borane derivative is a template which permits the stereospecific synthesis of complex structures. Other organoboranes are of interest for selective reductions. Still others are promising as blocking agents in carbohydrate and protein synthesis. The organoboranes provide a virgin new area of immense potential for application to problems in the biochemical and pharmaceutical areas.